Well, given the choices, I voted for Hard Rock, because it has some nice splurge items on the menu and the atmosphere tops NBA City IMHO. (Although food at NBA is also first-rate).
That said, I don't really think any of the choices are "anniversary" quality restaurants. The ones I'd single out for a very special meal are Delfino Riviera at PBH, Emeril's at CityWalk and Tchoup Chop at RPR. Of course, the downside of these choices is that they are all quite expensive.